In recent years, increased recognition of the many benefits of cardiovascular and aerobic exercise and body conditioning, in combination with continually increasing time constraints of modern lifestyles have resulted in a large demand for exercise devices which can provide maximum benefits of exercise with a minimum of inconvenience and minimum time requirement. This demand has resulted in the development of numerous types of exercise machines and systems.
Exercise machines and systems may be categorized based upon the method and medium utilized to provide a resistive force against which the muscles are worked and the configuration of the structural elements of the apparatus through which the user athlete interfaces with the resistive medium. Prior to the advent of modem exercise machines and universal gyms, iron weights lifted against gravity were the most common resistance medium. There is an ever present danger associated with the use of such free weight equipment that a user athlete will lose control of the weight due to fatigue of the athlete's muscles or an attempt to lift more weight than the athlete's muscles are capable of controlling. Much time is required for changing weights and moving weights and auxiliary equipment to prepare for different exercises. Many contemporary exercise and universal gym devices continue to use iron weights, or weights made of other suitably dense material, to provide resistance for muscle exercise while attempting to overcome the dangers and inconvenience of free weight exercise apparatus. These devices confine the weights to movement along fixed tracks to eliminate dangers associated with loss of control and dropping of free weights during attempts to work the muscles against too great a force. The weights of these apparatus are connected by chains, levers and the like, in various configurations, to exercise members which are engaged and worked in a cyclical fashion during muscle conditioning exercises by the user athlete. These machines, however, also suffer from a number of disadvantages. First, they must be massive to provide the weight necessary for training advanced athletes and to provide the structural strength necessary to support and control that weight. Also, they are complex because all exercising motions must be translated into up and down movement of the weights along their tracks in the gravitational field.
Efforts to reduce the great mass associated with weight resistance devices and to free the design of exercise machine and universal gym structures from the constraints of orienting the movement of the resistance medium to an alignment with gravity have lead to the development of a number of exercise devices based upon hydraulic resistance. While machines of this type differ in their hydraulic system design and their structural configuration for providing the interface between the user athlete and the hydraulic resistance system, the hydraulic systems of all these apparatus generally have two key elements in common; a hydraulic cylinder with a piston linked to an exercise member and arranged to pump fluid in and out of the cylinder in response to movement of the exercise member through an exercise cycle, and a static and/or dynamic flow resistance means for creating a resistive pressure in the cylinder against which the muscles are worked.
Most hydraulic exercise apparatus heretofore known in the art utilize double-action hydraulic cylinders. The utilization of double-action hydraulic cylinders in many of these devices results in multi-directional resistance. That is, unlike exercise with free weights, exercising forces are provided by double-action cylinder devices which resist movement of the exercise member during both an exercise stroke and a return stroke of an exercise cycle. Due to this “two-way resistance”, these devices fail to provide the benefits of muscle exercise which may be obtained with “free weight” exercising apparatus which do not provide a resisting force during the return stroke. Double-action cylinders are more complex and costly than single-action hydraulic cylinders, and are generally weaker than single-action hydraulic cylinders of similar cost and size. Thus, in devices using double-action cylinders, the cylinders must be located further from fulcrum points requiring larger structures than can be provided by exercise devices utilizing single-action cylinders.
Many hydraulic exercise devices of the present art also lack sufficient configuration adaptability to provide a full range of individual muscle toning exercises necessary for true muscle conditioning program versatility. Many of these machines utilize designs requiring the use of multiple single-action hydraulic cylinders in order to allow a reasonable number of different exercises to be accomplished with the aid of only that single machine, further increasing its mass and complexity. In U.S. Pat. No. 5,058,887; this inventor disclosed a hydraulic exercise apparatus utilizing a single-action hydraulic cylinder which provided a great variety of exercises to be performed with a simple and versatile exercise resistance assembly. However, this assembly required removal from and reattachment to the exercise resistance assembly for certain exercise devices to achieve reversal of the exercise resistance force direction.